The present invention relates to a heavy duty tire of which tread wear resistance is improved.
Recently, heavy duty cars such as trucks, buses and the like are required to run at a high speed because the expressway networks are improving. Also it is desired to reduce running costs. Therefore, the tires used in such heavy duty cars are required to have a highly improved tread wear resistance.
On the other hand, when the tread of a heavy duty tire is worn and the depth of the tread grooves reaches about 50%, the tread life has reached its end. This type of tread life is called the first life.
In general, in order to improve drainage and wet grip performance, a heavy duty tire is provided with circumferential grooves defining a tread pattern, and a five-rib pattern comprising four circumferential grooves as shown in FIG. 6(A) and (B) has been widely used.
In such a five-rib pattern, however, uneven wear (shown in FIG. 6(B) by parallel-hatching) is caused along the edges of the circumferential grooves (a), which greatly shortens the first life.
Also, a three-rib pattern comprising two circumferential grooves (a), for example as shown in FIG. 7, has been used since the rib is increased in the rigidity, which is of great advantage in preventing wear, but no advantage in providing grip performance.